During the past several years, the nanoparticle and the chemical substance tagged by a special material have been widely used to conduct the researches in the metabolism, distribution and bind, etc., of a biomolecule and small amount of synthetic material in the biochemistry field. Remarkably, there are several methods for using the radioactive isotope, the organic phosphor and the inorganic quantum dot (Qdots).
In the method using the radioactive isotopes, 3H, 14C, 32P, 35S, 125I, and the like, which are the radioisotopes of 1H, 12C, 31P, 32S, 127I and the like which are generally discovered in an organism, are widely used. Since the chemical characteristics of the radioactive isotopes are almost the same as that of the non-radioactive isotopes, it is possible to make an arbitrary substitution and they have the advantages in that emitting energy is relatively high and then the detection can be made by a small amount thereof. Therefore, the radioactive isotopes have been used for a long time in the different fields. However, it is hard work to handle them in the human body because of the radiation. In addition, they have the disadvantage of being inconvenient in safekeeping with a person or the experiment for the long time because of a short half life even if the emitting energy is high.
Organic fluorescent dyes are widely used as an alternative of the radioactive isotopes. The organic fluorescent dyes radiate the light which has a specific wavelength when they are activated by a specific wave. Particularly, as a detecting method is carried out in a miniaturized apparatus, the detection of the radioactive substance is limited in an amount and the long time is required for the detection. Meanwhile, in case of the organic fluorescent dyes which can emit a few thousand photons per molecule in an appropriate condition, it is possible to detect a few photons on a mono-molecular level, theoretically. However, being different from the radioactive isotopes, the organic fluorescent dyes have limitations in that it is not possible to directly substitute an element of the active ligand with others and a part, which does not relatively affect the activity, has to be connected to the organic fluorescent dyes through the structure-activity relation. Moreover, the organic fluorescent dyes have disadvantages in that the fluorescence intensity of these fluorescent marker materials is gradually weak (photobleaching) as time goes on and an interference between the different fluorescent materials is generated because the wavelength of the emitted light is very broad. Further, the fluorescent materials to be used are exceedingly limited in numbers.
On the other hand, a quantum dot, which is the semiconductor nanostructure, is composed of CdSe, CdS, ZnS, ZnSe, etc., and these radiate different colors of the light according to the size and kind of the nanostructure. As compared to the organic fluorescent dyes, since the quantum dot has a broad activating wavelength and a narrow emitting wavelength, the number of colors of the light from the semiconductor nanostructure is lager than that from the organic fluorescent dyes. Therefore, recently, the quantum dot is very much used as a method for overcoming the disadvantages of the organic fluorescent dyes. However, it has strong toxicity and the mass production is hard. Further, the large number of kinds of the quantum dots can be used, theoretically; however, the quantum dots which are actually used are exceedingly limited in numbers.
To solve the problem, a tagging material using the surface enhanced Raman scattering method has been recently used. Typically, there is introduced a method for using 5 to 10 nm gold nanoparticles and DNA in order to make a surface enhanced Raman scattering tagging material. First, after introducing a thiol group having a strong affinity with the gold nanoparticles to the 3′ ends of DNA, Cy3, Cy3.5, and Cy5 are respectively introduced as the tagging materials and a ligand capable of recognizing a specific biomass is introduced into the 5′ end of DNA. The DNA which is modified as set forth above is introduced onto the gold nano surface and this is used as the tagging material. After this surface enhanced Raman scattering gold nano-tagging particles reacts on a target biomass, they are analyzed after the strong Raman activity based on the silver ions. However, this method has the disadvantage in that it is hard to modify the DNA and the cost is high to reform DNA used as the tagging material.